1. Field of the Invention
The invention described herein is related to the conversion of heavy crude feedstocks of high molecular weight which are characterized by high metal, sulfur, conradson carbon and asphaltenes content. This invention more specifically is a method to be applied to catalytic slurry process where a catalyst or additive is employed in the presence of hydrogen in order to convert hydrocarbonaceous feedstocks, such as the Orinoco Belt Crudes, Maracaibo Lake Crudes, tar sands of Athabasca and Canadian crude oils like Cold Lake. These crudes have a sulfur content of between 2 and 6%, a metal content (V+Ni) of between 200 and 1400 ppm or more, a density less than 20.degree. API, conradson carbon of more than 2% and a boiling fraction of 500.degree. C..sup.+ higher than 40 wt.%.
2. Discussion of Background
Depending on the conversion rate and hydrocracking operating conditions (pressure, temperature, gas/oil ratio etc.) and the tendency of the feedstock to produce coke; a catalyst or additive such as activated coke from hard coal or lignite, carbon black (soot), red mud, iron (III) oxide, blast furnace dust, ashes from gasification processes of crude oil mentioned before, natural inorganic minerals containing iron, such as laterite or limonite, amounting to from 0.5 to 15 wt.% of the liquid or liquid/solid feedstock is used in these slurry hydrogenation processes.
EP No. 0073527, representing one of the latest development in technology, describes a catalytic treatment of heavy and residue oils in the presence of lignite coke which is mixed with catalytically active metals, preferably with their salts, oxides or sulfides or dust which is produced in the gasification of lignite, in a concentration of between 0.1 and 10 wt.% with respect to the heavy and residue oils. This catalyst or additive is used in the finest distribution with particle sizes of, for example, less than 90-100 microns.
U.S. Pat. No. 3,622,498 also describes a process that teaches that the asphaltene containing hydrocarbonaceous feedstock may be converted by forming a reactive slurry of the asphaltenes--containing the hydrocarbonaceous feedstock, hydrogen and a finely divided catalyst containing at least one metal from the group VB, VIB or VIII and reacting the resulting slurry at 68 bar and 427.degree. C.
U.S. Pat. No. 4,396,495 describes a process for the conversion in slurry reactors of hydrocarbonaceous black oil using a finely divided, unsupported metal catalyst like vanadium sulfide with a particle size of between 0.1 and 2000 microns, a preferred range of 0.1 to 100 microns, where an antifoaming agent based on silicone is also fed to the conversion zone to reduce the foam formation that is produced at the conditions where the reaction takes place (temperature up to 510.degree. C., pressure of about 204 bar and catalyst concentration of about 0.1 wt.% to 10 wt.%). This method is not adequate for temperatures higher than about 430.degree. C.; due to the decomposition of the silicone as this loses its activity, also the silicone agent remains in the low boiling point fractions producing difficulties in the upstream processing.
Canadian Pat. No. 1,117,887 describes a hydrocracking process for the conversion of heavy oils to light products where high pressure and temperature are employed. The heavy oil is put in contact with a catalyst which is finely divided coal carrying at least one metal of group IVA or VIII of the periodic table where the coal is a subbituminous coal having a particle size of less than 100 mesh (&lt;149 microns).
U.S. Pat. No. 4,591,426 which also describe a process of hydroconversion of heavy crudes with at least 200 ppm metal content using natural inorganic materials as a catalyst such as laterite or limonite which have a particle size of between 10 and 1000 microns at temperatures higher than 400.degree. C. and total hydrogen pressure of 102 bar.
When the reactor zone is a moving bed-reactor, feeding an amount of 1.0 to 15 wt.% based on the feedstock where the reactants in said reaction zone are between 20 wt.% and 80 wt.% and a particle size of between 1270 and 12700 microns is employed.
Those skilled in the art of hydrocarbon processing have not recognized that under conditions which are normally used in catalytic slurry reactors of the bubble column type, using inexpensive catalysts or additives like these previously described may produce foam, which reduces the amount of liquid in the reaction zone when higher gas velocities of more than 3 cm/sec are employed. These higher gas velocities are also employed in industrial reactors.